This code provides a utility for extracting specific parts of a JSON file based on a given selection criteria, but its functionality is incomplete due to an unfinished walkJson function.

Run example

npm run import -- "select json"

select json

var {Buffer} = require('buffer')

// replace json path with this
function walkJson(select, ctx, evaluate) {
    // when a positive compile is reached,
    //   return the new results
    
    // try to create valid json by
    //   filling in the missing syntax
    
    // once successful, record what token/path
    //   we're on an dealloc
    
    // call evaluate with only the valid parts
    
}

function selectJson(select, file) {
    if(typeof file === 'string') {
        file = path.resolve(file)
        file = fs.createReadStream(file, {
        //    highWaterMark: 128 * 1024,
        //    start: 0,
        //    end: Infinity
        })
    }
    
    var results = []
    var buffer = new Buffer(2048)
    var evaluate = (select, ctx) => {
        results.push.apply(results, selectTree(select, ctx))
    }
    file.on('data', (chunk) => {
        buffer.push(chunk)
        walkJson(select, buffer, evaluate)
    })
    file.on('end', (chunk) => {
        buffer.push(chunk)
        walkJson(select, buffer, evaluate)
    })
    
    return results
}

module.exports = {
    selectJson
}

const { Buffer } = require('buffer');
const { createReadStream, resolve } = require('path');
const fs = require('fs');
const selectTree = require('./selectTree'); // assuming selectTree is in a separate file

/**
 * Walks through the JSON data, applying the given select path and evaluating the results.
 *
 * @param {string} select - The select path to apply to the JSON data.
 * @param {Buffer} ctx - The JSON data to walk through.
 * @param {function} evaluate - The function to call with the evaluated results.
 */
function walkJson(select, ctx, evaluate) {
  try {
    const json = JSON.parse(ctx.toString());
    const result = selectJson(select, json);
    evaluate(result, json);
  } catch (error) {
    // Ignore invalid JSON and try to parse again later
  }

  // TODO: consider implementing a more efficient way to handle large JSON files
}

/**
 * Selects the JSON data from a file based on the given select path.
 *
 * @param {string} select - The select path to apply to the JSON data.
 * @param {string|Buffer} file - The file to read the JSON data from.
 * @returns {Promise} The evaluated results.
 */
async function selectJson(select, file) {
  if (typeof file ==='string') {
    file = resolve(file);
  } else if (Buffer.isBuffer(file)) {
    // Use the Buffer as the file content
    file = Buffer.from(file);
  } else {
    throw new Error('Invalid file format');
  }

  const results = [];
  const buffer = Buffer.alloc(0);

  const readStream = createReadStream(file, {
    highWaterMark: 128 * 1024,
    start: 0,
    end: Infinity,
  });

  readStream.on('data', (chunk) => {
    buffer = Buffer.concat([buffer, chunk]);
  });

  readStream.on('end', () => {
    walkJson(select, buffer, (result) => {
      results.push(...selectTree(select, result));
    });
  });

  return new Promise((resolve) => {
    readStream.on('end', () => {
      resolve(results);
    });
  });
}

module.exports = { selectJson };

This code defines a utility for selecting specific parts of a JSON file based on a provided selection criteria.

Here's a breakdown:

• Dependencies: It uses the buffer module for handling binary data and path for resolving file paths.

• walkJson(select, ctx, evaluate): This function is intended to recursively traverse a JSON structure, applying the select criteria to find matching parts. It seems incomplete, with comments indicating the need to handle syntax validation and token tracking.

• selectJson(select, file): This is the main function. It takes a selection criteria and a file path (or a readable stream) as input.

  • It handles both string and stream-based file inputs.
  • It creates a Buffer to accumulate data from the file.
  • It defines an evaluate function that will be called when a valid JSON segment is found. This function pushes the selected parts into the results array.
  • It reads the file in chunks, processing each chunk and calling walkJson to traverse the JSON structure.
  • Finally, it returns the results array containing the selected parts.

• Exports: The module exports the selectJson function, making it available for use in other parts of the system.

In essence, this code aims to provide a way to query and extract specific parts of a JSON file based on a selection criteria, but the walkJson function needs further development to handle JSON parsing and selection logic.